Re: [PATCH] dt-bindings: virtio: Convert virtio,pci-iommu to DT schema

[Krzysztof Kozlowski]

On 16/09/2022 14:22, Jean-Philippe Brucker wrote:
> Convert the binding that describes the virtio-pci based IOMMU to DT
> schema. Change the compatible string to "pci<vendor>,<device>", which is
> defined by the PCI Bus Binding, but keep "virtio,pci-iommu" as an option
> for backward compatibility.
> 
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
> ---
>  .../devicetree/bindings/virtio/iommu.txt      | 66 --------------
>  .../devicetree/bindings/virtio/iommu.yaml     | 86 +++++++++++++++++++
>  2 files changed, 86 insertions(+), 66 deletions(-)
>  delete mode 100644 Documentation/devicetree/bindings/virtio/iommu.txt
>  create mode 100644 Documentation/devicetree/bindings/virtio/iommu.yaml
> 
> diff --git a/Documentation/devicetree/bindings/virtio/iommu.txt b/Documentation/devicetree/bindings/virtio/iommu.txt
> deleted file mode 100644
> index 2407fea0651c..000000000000
> --- a/Documentation/devicetree/bindings/virtio/iommu.txt
> +++ /dev/null
> @@ -1,66 +0,0 @@
> -* virtio IOMMU PCI device
> -
> -When virtio-iommu uses the PCI transport, its programming interface is
> -discovered dynamically by the PCI probing infrastructure. However the
> -device tree statically describes the relation between IOMMU and DMA
> -masters. Therefore, the PCI root complex that hosts the virtio-iommu
> -contains a child node representing the IOMMU device explicitly.
> -
> -Required properties:
> -
> -- compatible:	Should be "virtio,pci-iommu"
> -- reg:		PCI address of the IOMMU. As defined in the PCI Bus
> -		Binding reference [1], the reg property is a five-cell
> -		address encoded as (phys.hi phys.mid phys.lo size.hi
> -		size.lo). phys.hi should contain the device's BDF as
> -		0b00000000 bbbbbbbb dddddfff 00000000. The other cells
> -		should be zero.
> -- #iommu-cells:	Each platform DMA master managed by the IOMMU is assigned
> -		an endpoint ID, described by the "iommus" property [2].
> -		For virtio-iommu, #iommu-cells must be 1.
> -
> -Notes:
> -
> -- DMA from the IOMMU device isn't managed by another IOMMU. Therefore the
> -  virtio-iommu node doesn't have an "iommus" property, and is omitted from
> -  the iommu-map property of the root complex.
> -
> -Example:
> -
> -pcie@10000000 {
> -	compatible = "pci-host-ecam-generic";
> -	...
> -
> -	/* The IOMMU programming interface uses slot 00:01.0 */
> -	iommu0: iommu@0008 {
> -		compatible = "virtio,pci-iommu";
> -		reg = <0x00000800 0 0 0 0>;
> -		#iommu-cells = <1>;
> -	};
> -
> -	/*
> -	 * The IOMMU manages all functions in this PCI domain except
> -	 * itself. Omit BDF 00:01.0.
> -	 */
> -	iommu-map = <0x0 &iommu0 0x0 0x8>
> -		    <0x9 &iommu0 0x9 0xfff7>;
> -};
> -
> -pcie@20000000 {
> -	compatible = "pci-host-ecam-generic";
> -	...
> -	/*
> -	 * The IOMMU also manages all functions from this domain,
> -	 * with endpoint IDs 0x10000 - 0x1ffff
> -	 */
> -	iommu-map = <0x0 &iommu0 0x10000 0x10000>;
> -};
> -
> -ethernet@fe001000 {
> -	...
> -	/* The IOMMU manages this platform device with endpoint ID 0x20000 */
> -	iommus = <&iommu0 0x20000>;
> -};
> -
> -[1] Documentation/devicetree/bindings/pci/pci.txt
> -[2] Documentation/devicetree/bindings/iommu/iommu.txt
> diff --git a/Documentation/devicetree/bindings/virtio/iommu.yaml b/Documentation/devicetree/bindings/virtio/iommu.yaml
> new file mode 100644
> index 000000000000..d5bbb8ab9603
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/virtio/iommu.yaml
> @@ -0,0 +1,86 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/virtio/iommu.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: virtio-iommu device using the virtio-pci transport
> +
> +maintainers:
> +  - Jean-Philippe Brucker <jean-philippe@xxxxxxxxxx>
> +
> +description: |
> +  When virtio-iommu uses the PCI transport, its programming interface is
> +  discovered dynamically by the PCI probing infrastructure. However the
> +  device tree statically describes the relation between IOMMU and DMA
> +  masters. Therefore, the PCI root complex that hosts the virtio-iommu
> +  contains a child node representing the IOMMU device explicitly.
> +
> +  DMA from the IOMMU device isn't managed by another IOMMU. Therefore the
> +  virtio-iommu node doesn't have an "iommus" property, and is omitted from
> +  the iommu-map property of the root complex.
> +
> +properties:
> +  # If compatible is present, it should contain the vendor and device ID
> +  # according to the PCI Bus Binding specification. Since PCI provides
> +  # built-in identification methods, compatible is not actually required.
> +  compatible:
> +    oneOf:
> +      - items:
> +          - const: virtio,pci-iommu
> +          - const: pci1af4,1057
> +      - items:
> +          - const: pci1af4,1057
> +
> +  reg:
> +    description: |
> +      PCI address of the IOMMU. As defined in the PCI Bus Binding
> +      reference, the reg property is a five-cell address encoded as (phys.hi
> +      phys.mid phys.lo size.hi size.lo). phys.hi should contain the device's
> +      BDF as 0b00000000 bbbbbbbb dddddfff 00000000. The other cells should be
> +      zero. See Documentation/devicetree/bindings/pci/pci.txt
> +
> +  '#iommu-cells':
> +    const: 1
> +
> +required:

Also: compatible

> +  - reg
> +  - '#iommu-cells'
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    pcie0 {

Node name: pcie

> +        #address-cells = <3>;
> +        #size-cells = <2>;
> +

device_type and then you will see a bunch of warnings.

> +        /*
> +         * The IOMMU manages all functions in this PCI domain except
> +         * itself. Omit BDF 00:01.0.
> +         */
> +        iommu-map = <0x0 &iommu0 0x0 0x8
> +                     0x9 &iommu0 0x9 0xfff7>;
> +
> +        /* The IOMMU programming interface uses slot 00:01.0 */
> +        iommu0: iommu@1,0 {
> +            compatible = "pci1af4,1057";
> +            reg = <0x800 0 0 0 0>;
> +            #iommu-cells = <1>;
> +        };
> +    };
> +
> +    pcie1 {

Node name: pcie (so probably you will need unit address and reg)

> +        /*
> +         * The IOMMU also manages all functions from this domain,
> +         * with endpoint IDs 0x10000 - 0x1ffff
> +         */
> +        iommu-map = <0x0 &iommu0 0x10000 0x10000>;
> +    };
> +
> +    ethernet {
> +        /* The IOMMU manages this platform device with endpoint ID 0x20000 */
> +        iommus = <&iommu0 0x20000>;
> +    };
> +
> +...


Best regards,
Krzysztof